Short-Throw Projectors Fill the Screen from Up Close

A new breed of projectors with short-throw capabilities lets your laptop and projector remain close to the screen rather than back in the audience. With a short-throw projector, it’s harder to cast your shadow on the screen or for the audience to trip over cables or for restless students to jostle a projector cart. With a price premium of as little as 15% over a comparable normal throw projector, short- and ultra-short projectors now make up almost one in five projector sales. Classrooms are the primary drivers for short-throw projectors, along with businesses and gamers.

“With short-throws now, you’re not getting many tradeoffs” says Chris Chinnock, president of the Insight Media consulting firm. “They’re a little more expensive but you don’t lose much brightness or crispness. So it’s more of a personal preference which you choose.”

Short Throw: Fill Most Screens from Just a Few Feet Away With the first portable data projectors of the 1990s, the projector had to be 15 to 20 feet back to fill an 8-foot screen. The distance from projector to screen compared to the screen size is the projector’s throw ratio. If the projector is 12 feet back and it fills an 8-foot screen, that’s a 1.5:1 throw ratio, or just 1.5. A short-throw projector has a ratio of less than 1, down to about 0.4, meaning you could fill a 8-foot screen with the projector as little as 3.5 feet away. Most are in the 0.6 to 0.8 range. Ultra-short-throw projectors have a throw ratio of less than 0.4.

Education Drives the Short-Throw Market

“Education is the main driving force behind the short throw market,” says Keith Yanke, NEC Display Solutions’ director of product marketing. “Installation and integration is usually cheaper when using a short throw model because you are installing the projector to the wall and not on the ceiling. This means lower mount costs, lower cable costs and less labor.”

Infocomm’s Chinnock agrees: “The strongest [growth] engine is education. There’s a lot of activity outside the U.S. and China is a major market.”

With ultra-short throw projectors, the unit can be mounted above the projection surface on an arm less than three feet long. Or it can go on a desk almost up against the wall.

How They Do It: Good Lenses, Pre-Warping ChipsTo make short-throw and ultra-short-throw projectors project usable images, says Chinnock, the manufacturer either uses a higher quality lens, or a chipset from a supplier such as Geo Semiconductor that pre-warps the image, or applies geometry corrections that cancel out the warping and keystoning inherent in wide-angle lenses that are tilted away from the level.

Either way, it raises the cost (notice the big lens on the short-throw projector above). NEC’s Yanke says a short throw projector costs 15%-20% more than a similar unit with normal throw while ultra-short-throw projectors have a 60%-70% premium.

How to Measure Short Throw (Good Luck Finding Common Ground)

Throw ratio has a simple definition – projector distance from screen vs. screen size – but it gets complicated quickly. Most people probably think of the throw ratio as the distance compared to the screen width. But in the tradition of TV sets that measure the screen diagonal, some projector makers measure throw the TV-set way: distance vs. screen diagonal. Within the industry, that may make sense, since screens are typically sold by their diagonal measurement, and it also makes the throw ratio seem better (by 10% to 25%).

For users who aren’t industry insiders, the distance-vs.-screen-diagonal definition is problematic twice over: Tripod-mount screens are typically squares, so the big 8-foot screen has a 96-inch diagonal and 68 inches of width. Also, since you’re not projecting a square image, the diagonal could vary from 77 to 85 inches, depending on the aspect ratio of the laptop or other device sending the image. (If the screen were 8′ wide as in the illustration above, the diagonal could be anywhere from 108 inches (16:9 display) to 120 inches.)

Epson, the industry sales leader, measures throw ratio as distance vs. diagonal, as do many others. Competitor NEC measures it as distance vs. screen diagonal. Infocomm’s Chinnock agrees that there’s little agreement. A number of reviewers and websites prefer the distance-vs.-screen-width definition because the throw ratio doesn’t change depending on the projector’s aspect ratio, and because if you walk into a facility to prepare for a presentation, you’re likely to measure the width of a screen.

How Can They Confuse You? Let Us Count the Ways I spent an intense couple weeks researching projectors recently and found that even with the help of pcmag.com’s projector reviews guru, M. David Stone, I found facts weren’t always facts when reading up online. Here’s what can be confusing:

Throw ratio. It varies up to 25% depending on which definition a manufacturer uses.

Projector-to-screen distance. With ultra-short-throws, the manufacturer may list the distance from front of projector to screen, while the lens is at the back, 12 to 18 inches from the wall.

Measurement units. Some manufacturer sites list the distance in meters and the screen size, often the diagonal, in inches. That’s in case you weren’t confused enough.

Lumens. Claimed light output can vary dramatically from actual output, which is why pcmag.com actually measures the output. A projector claiming 3,000 lumens may actually output 2,000 to 2,500 lumens on our instrumented tests. Or it might come in very close to spec.

Cheat Sheet for Throw Ratios If you agree that distance vs. screen width makes more sense when defining throw ratio, here’s how to correct a throw ratio expressed as distance vs. screen diagonal, assuming you can figure out which throw ratio definition a manufacturer uses (good luck).

4:3 ratio. If you have a traditonal 4:3 aspect ratio projector, multiply the throw ratio by 1.25 to get the distance-vs.-screen-width throw ratio. If a projector is listed as having a 0.6 throw ratio (distance vs. screen diagonal), it’s really 0.75 if you want to know distance vs. screen width. (The screen width is 80% of the diagonal (remember the 3-4-5 right triangle from high school math?) and the inverse is 1.25, which is the multiplier). 4:3 is the same as 16:12.

16:10 ratio. Multiply the throw ratio by 1.19 (1.2 is close enough).

16:9 ratio. Multiply the throw ratio by 1.13 (1.1 is close enough).

As a practical matter, with the increasingly popular 16:10 projectors, when you’re less than 10 feet away, the difference between the two ways of measuring throw ratio is about the same as difference between the front and back of a desk the projector may be sitting on. Just move the projector back (or forward).

Epson offers a good, if somewhat complex, distance-vs.-width calculator online. It’s pre-loaded with Epson projector models but also works fine for determining projector placement generally if you know the screen size, distance, or throw ratio (any two). You can even take into account screen height and ceiling height.

Other Projector Trends If you haven’t shopped for projectors in a couple years, much has changed:

Rise of the 16:10 projector. This mirrors the rise of the widescreen laptop. The most common widescreen projector resolution is 1280-by-800 pixels, a 30-percent pixel count improvement on the traditional 1024-by-768 pixel, 4:3 ratio projector.

Normal projectors approaching 1:1 throw ratios. According to Sara Kim and Heather Johnston, product managers at Epson America, the Epson PowerLite 1735W, a 16:10 widescreen projector, has a throw ratio of 0.98, and it’s considered a standard not short throw projector.

Standalone operation. With some projectors, if you plug in a USB key with photos, the projector plays them automatically; some can also play PC-created movie files, which could be, for instance, a PowerPoint saved in a movie format.

That’s in addition to the usual improvements you expect from technology over time: lighter weight, lower price, and more brightness (Epson at InfoComm showed a 4,000-lumen XGA projector, the Epson VS400, for $999). Optical zoom, often 1.2X, continues to be common on normal and some short throw projectors; on ultra-short-throw projectors, you zoom by moving the projector in or out a couple inches.

Recent Short Throw ProjectorsSeveral short-throw projectors were announced this spring, including at the recent InfoComm show. They include:

Epson BrightLink 450Wi ($2,199), an ultra-short-throw, 2,500 lumen, projector that can project an image 60 inches diagonal (about 4 feet wide) with the front of the projector just 3 inches from the screen.